Goldfish

Systematic position: The goldfish (Carassius auratus) belongs to the order Cypriniformes and the family Cyprinidae. While often perceived as a household pet, in open water systems, this species acts as an aggressive invasive pest that poses a significant threat to native aquatic environments.

Crops damaged: The goldfish causes extensive damage to aquatic and semi-aquatic vegetation in artificial ponds, rice paddies, and ornamental aquatic plant nurseries. It consumes tender shoots of lilies, hornwort, and duckweed, while simultaneously uprooting mature plants, which leads to total habitat degradation.

Biology and life cycle: This species is characterized by remarkable adaptability to fluctuating water conditions, including low oxygen levels and temperature extremes. Reproduction typically occurs during spring, with eggs attached to submerged vegetation. The species exhibits high fecundity, facilitating rapid colonization of new water bodies and competitive displacement of native species.

Character of damage and harmfulness: As a bottom feeder, the goldfish churns up sediment, which dramatically increases water turbidity. This prevents light penetration necessary for photosynthesis, effectively starving surrounding vegetation. Beyond physical destruction, the species alters water chemistry, making it toxic or inhospitable for specialized aquatic crops.

Protection measures: Managing this pest requires a strategic approach centered on exclusion and removal. Recommended practices include:

• Installing fine mesh barriers at water inlets and outlets to prevent migration.
• Periodic drainage and bottom disinfection of nurseries.
• Selective removal via traps or electrofishing to reduce population pressure.
• Introducing native predatory fish to regulate goldfish numbers in larger water bodies.

Professional monitoring and strict control of intentional or accidental introductions are essential to safeguard aquatic plant production and ecological health.